Vertebral body replacement device and method for use to maintain a space between two vertebral bodies within a spine

ABSTRACT

A vertebral body replacement device includes a first member and a first footplate detachably connectable to the first member, a second member and a second footplate detachably connectable to the second member, and a central member detachably connectable to the first member. The first member is displaceable relative to the second member in response to rotation of the central member relative to the first member to adjust the length of the vertebral body replacement device. The first footplate includes a first surface oriented toward the first member, a second surface oriented away from the first member, and a sidewall extending between the first surface and the second surface. The first surface includes an alignment slot facing the first member. The alignment slot is open through the sidewall of the first footplate and configured to slidingly engage the first member to orient the first footplate relative to the first member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/222,862, filed Mar. 24, 2014, now pending, which is a continuation ofU.S. application Ser. No. 13/900,782, filed May 23, 2013 and now issuedas U.S. Pat. No. 8,690,950, which is a continuation of U.S. applicationSer. No. 13/475,279, filed May 18, 2012 and now issued as U.S. Pat. No.8,591,587, which is a continuation-in-part of U.S. application Ser. No.11/928,532, filed Oct. 30, 2007 and now issued as U.S. Pat. No.8,182,537, and a continuation-in-part of U.S. application Ser. No.13/312,486, filed Dec. 6, 2011 and now issued as U.S. Pat. No.8,702,719, which is a continuation of U.S. application Ser. No.12/252,552, filed Oct. 16, 2008 and now issued as U.S. U.S. Pat. No.8,142,441. The contents of all of the foregoing applications and issuedpatents are incorporated by reference herein in their entireties and forall purposes.

TECHNICAL FIELD

The present invention relates generally to orthopaedic and neurosurgicalimplants used for insertion within the spine, and more specifically, butnot exclusively, concerns devices implanted within the spinal column toreplace a resected, fractured or diseased vertebral body and to maintainor reestablish proper spacing between the remaining adjacent vertebralbodies.

BACKGROUND

Damage or disease that affects the integral structure of a vertebralbody within an individual's spinal column may lead to neurologicimpairment with possible permanent damage to the spinal cord as well asimproper neck and back alignment. Maintaining anatomic spacing withinthe spinal column is critical to ensuring continued functionality of thespinal cord and nerve roots and avoidance of long term seriousneurological impairment.

Typically, spinal implants that are used as a spacer type of device havea fixed overall length and are implanted without the ability to adjustthe degree of expansion or curvature. Recent developments of spinalspacers have resulted in devices that may be lengthened in vivo byrotary motion to match the space presented by the missing vertebralbody. In use, these spinal spacers can be expanded until the height ofthe spacer reaches the height of the disc space in which the spacer isinserted. Problems that have been seen with these types of designsinclude post-placement migration attributable to the forces applied tothe implant during use risking the patient to neurologic injury. Theproper sizing of the implant relative to the presented clinical spaceand the achievement of optimum expansion are important to ensure thatthe implant fills the space and does not loosen or migrate postimplantation. To achieve the required distraction, it is important thatthe implant insertion and distraction instrument provides the user withoptimum handling characteristics. Suitable device access ports forheight manipulation are very important, as are a good assortment ofendplate angulation possibilities.

Spacers that are lengthened by rotary motion may include gear mechanismsthat are engaged by and rotated by a driver tool. For some of thesespacers, surgeons rely at least in part on tactile feel to determinewhen the spacer is fully expanded; i.e. when the ends of the spacercontact the vertebrae on either side of the disc space. In an idealoperation, the gear mechanism rotates with very little resistance untilthe ends of the implant contact the adjacent vertebrae. Once contactoccurs, the device exhibits resistance to further expansion, and thatresistance can be sensed by the surgeon as a signal that the implant isfully expanded in the disc space. If the gear mechanism does not rotateproperly, due to improper engagement with the driver tool, damaged gearteeth, or other reason, then the surgeon may sense resistance from theimplant before the implant is completely expanded, referred to herein as“premature resistance”. Premature resistance can make it difficult orimpossible for the surgeon to sense precisely when the implant is fullyexpanded in contact with the adjacent vertebrae. In some cases,premature resistance from the implant can be mistaken as a signal thatthat the implant is completely expanded, when in fact it is not.

SUMMARY

The drawbacks of known vertebral body replacement devices are addressedin many respects by vertebral body replacement devices in accordancewith the invention.

In one embodiment, a vertebral body replacement device may include abody member having an outer wall for engagement with a tool. The outerwall may include a plurality of tool ports arranged along at least aportion of a perimeter of the body member. The vertebral bodyreplacement device may also include a central rod member configured tobe operatively associated within the body member. The central rod membermay have a first threaded portion, a second threaded portion, and a gearwheel portion. The gear wheel portion may include a toothed surface anda support surface. The vertebral body replacement device may furtherinclude a first end member and a second end member. The first end membermay be configured to threadingly engage the first threaded portion ofthe central rod member, and the second end member may be configured tothreadingly engage the second threaded portion of the central rodmember.

The body member, first end member and second end member may beconfigured to inhibit rotational movement of the first and second endmembers when the vertebral body replacement device is disposed within aspace within a spinal column with the first and second end membersengaging respective vertebral bodies of the spinal column and thecentral rod member is rotationally actuated to move the first end memberand the second end member in an axial direction relative to the bodymember allowing for the first end member and the second end member toapply a force to the two vertebral bodies to maintain a desired spacetherebetween.

The plurality of tool ports may include a first tool port, a second toolport and a third tool port. The third tool port may be positionedbetween the first and second tool ports, with the toothed surface of thegear wheel portion exposed through the third tool port when the centralrod member is operatively associated within the body member. Inaddition, the third tool port may be configured to receive a tool thatengages the gear wheel portion.

The first tool port and the second tool port may collectively form analignment and indexing mechanism that allows a tool to be insertedthrough the third tool port and into proper engagement with the gearwheel portion. The first tool port and second tool port may eachcomprise an elongated slot. The first tool port and second tool port maybe equidistant from the first end member and the second end member.

The vertebral body replacement device may include a fourth tool portlocated in a position that is either superior to or inferior to thethird tool port. A locking screw may be housed inside the fourth toolport. The locking screw may include an outer thread and the fourth toolport may include an inner thread in engagement with the outer thread.The inner thread may terminate at a point within the fourth tool portthat is recessed inside and spaced from the outer wall to prevent thelocking screw from being removed from the tool port through the outerwall.

The vertebral body replacement device may also include a fifth toolport. The fourth tool port may be located in a position that is superiorto the third tool port, and the fifth tool port may be located in aposition that is inferior to the third tool port.

The vertebral body replacement device may further include a supportring. The support ring may include a bearing surface contacting thecentral rod member when the central rod member is operatively positionedwithin the body member. The support surface of the gear wheel portionmay be configured to contact the bearing surface of the support ringwhen the central rod member is operatively positioned within the bodymember.

The central rod member may include a central axis extending between thefirst threaded portion and the second threaded portion thereof. Arotational axis of the gear wheel portion is substantially coaxial tothe central axis of the central rod member. When the gear wheel portionis rotated about the rotational axis, the first and second threadedportions may correspondingly rotate about the central axis of thecentral rod member.

The vertebral body replacement device may also include at least onefootplate member. The at least one footplate member may couple to atleast one of the first end member and the second end member. The firstend member and the second end member may each include an external wall,an internal wall and an end wall. The first end member and the secondend member may also each include at least one travel limiting mechanismthat engages the body member to limit movement of the first end memberand second end member relative to the body member. The at least onetravel limiting mechanism may include a pin configured to slidinglyengage the body member.

At least one of the first end member and the second end member mayfeature at least one projection that is disposed on the end wall andextends in an outward direction. The first end member and the second endmember may each comprise at least one hole disposed in at least one ofthe external wall and the end wall and extending therethrough, therebyallowing for the placement of bio-compatible material within the firstand second end members. The body member may include an inner wall and atleast one hole extending from the outer wall through the inner walltherethrough, thereby allowing for the placement of bio-compatiblematerial within the body member.

The vertebral body replacement device may further include at least onefootplate member and a snap ring. The snap ring may detachably couplethe at least one footplate member at least one of the first end memberand the second end member.

Additional features and advantages are realized through the techniquesof the present invention. Other embodiments and aspects of the inventionare described in detail herein and are considered a part of the claimedinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary and the detailed description that follows will bebetter understood in conjunction with the accompanying drawing figures,of which:

FIG. 1 is a perspective, exploded view of one embodiment of a vertebralbody replacement device, in accordance with an aspect of the presentinvention;

FIG. 2A is a cross-sectional, side elevational view of an end member ofthe vertebral body replacement device of FIG. 1 taken along line 2-2,showing an inner portion with a surrounding external wall, an internalwall and an end wall with the inner portion including a centrallyoriented threaded housing element configured to engage a central rodmember with the end wall being oriented normal relative to the externalwall, in accordance with an aspect of the present invention;

FIG. 2B is a cross-sectional, side elevational view of an alternativeembodiment of an end member, showing an inner portion with a surroundingexternal wall, an internal wall and an end wall with the inner portionincluding a centrally oriented threaded housing element configured toengage a central rod member with the end wall being oriented at an anglerelative to the external wall, in accordance with an aspect of thepresent invention;

FIG. 3 is a cross-sectional, side elevational view of a body member ofthe vertebral body replacement device of FIG. 1 taken along line 3-3,showing two receptacle ends and internal threads for engaging a supportring, in accordance with an aspect of the present invention;

FIG. 4 is a side elevational view of a central rod member of thevertebral body replacement device of FIG. 1, in accordance with anaspect of the present invention;

FIG. 5 is a side elevational view of the assembled vertebral bodyreplacement device of FIG. 1, showing a superiorly positioned end memberand an inferiorly positioned end member extended away from the bodymember, in accordance with an aspect of the present invention;

FIG. 6 is a perspective view of the vertebral body replacement device ofFIG. 1, with a tool inserted through a tool port hole and in operableposition with the central rod member, in accordance with an aspect ofthe present invention;

FIG. 7 is a side elevational view of the vertebral body replacementdevice of FIG. 1, shown disposed within a space between two vertebralbodies within a spinal column prior to the translational movement of thesuperiorly positioned end member and the inferiorly positioned endmember, in accordance with an aspect of the present invention;

FIG. 8 is a side elevational view of the vertebral body replacementdevice of FIG. 1, shown positioned between two vertebral bodies with thesuperiorly positioned end member and the inferiorly positioned endmember extended to maintain a desired space within a spinal column, inaccordance with an aspect of the present invention;

FIG. 9 is a perspective view of an alternative embodiment of a vertebralbody replacement device, with a superiorly positioned, detachablefootplate member and an inferiorly positioned, detachable footplatemember shown prior to being coupled to the superiorly positioned endmember and an inferiorly positioned end member, respectively, inaccordance with an aspect of the present invention;

FIG. 10A is a side elevational view of a detachable footplate member ofthe vertebral body replacement device of FIG. 9, showing an end surfacebeing oriented normal relative to a sidewall, in accordance with anaspect of the present invention;

FIG. 10B is a side elevational view of an alternative embodiment of adetachable footplate member used with the vertebral body replacementdevice of FIG. 9, showing the end surface being oriented at an anglerelative to the sidewall, in accordance with an aspect of the presentinvention;

FIG. 11A is a perspective view of another alternative embodiment of adetachable footplate member;

FIG. 11B is a perspective view of another alternative embodiment of adetachable footplate member;

FIG. 12 is a perspective view of one embodiment of a surgicalinstrument, in accordance with an aspect of the present invention;

FIG. 13 is an enlarged, exploded perspective view of a distal end of thesurgical instrument of FIG. 12 showing the distal aspects of an elongatemember and a locking mechanism with an implant engagement assembly thatincludes an actuation body, a holding portion and an alignment body, inaccordance with an aspect of the present invention;

FIG. 14 is a side elevational view of the surgical instrument of FIG.12, in accordance with an aspect of the present invention;

FIG. 15 is a top view of the surgical instrument of FIG. 12, inaccordance with an aspect of the present invention;

FIG. 16 is an enlarged, side elevational view of the assembled distalend of the surgical instrument of FIG. 12 showing the elongate memberwith external threads, the locking mechanism with a bearing portion, theimplant engagement assembly, including the actuation body and holdingportion with engagement member and the alignment body, in accordancewith an aspect of the present invention;

FIG. 17 is an enlarged, top view of the assembled distal end of thesurgical instrument of FIG. 12 showing the elongate member with externalthreads, the locking mechanism with a coupling end, the implantengagement assembly, including the actuation body and the holdingportion that includes the first and second arms and correspondingengagement members and the alignment body. Also seen, is the distal endof a length control mechanism, including a gear assembly, in accordancewith an aspect of the present invention;

FIG. 18 is an enlarged, perspective view of the assembled distal end ofthe surgical instrument of FIG. 12 showing the elongate member, thelocking mechanism with the bearing portion, the implant engagementassembly including the actuation body and the holding portion thatincludes the first and second arms with the corresponding engagementmembers and the alignment body. Also seen, is the distal end of thelength control mechanism with the gear assembly, in accordance with anaspect of the present invention;

FIG. 19 a cross-sectional, perspective view of the surgical instrumentof FIG. 12 taken along line 19-19, showing a top portion of the handleassembly, the elongate member and the implant engagement assembly, thelength control mechanism and the locking mechanism, in accordance withan aspect of the present invention;

FIG. 20 is a perspective view of a spinal implant coupled to thesurgical instrument of FIG. 12, shown positioned prior to insertion intoa space between two vertebral bodies, in accordance with an aspect ofthe present invention;

FIG. 21 is a perspective view of the spinal implant coupled to thesurgical instrument of FIG. 12, shown positioned in a space between twovertebral bodies with the length control mechanism being rotated toextend the spinal implant to allow the ends to make contact with thesuperior and inferior vertebral bodies to maintain a desired spacingarrangement within a spinal column, in accordance with an aspect of thepresent invention;

FIG. 22 is an enlarged top view of distal end of the surgical instrumentof FIG. 12, showing the gear assembly inserted into the spinal implant,in accordance with an aspect of the present invention;

FIG. 23 is a perspective view of the spinal implant coupled to thesurgical instrument of FIG. 12, shown positioned in a space between twovertebral bodies following final length determination with the lockingmechanism being rotated, in accordance with an aspect of the presentinvention;

FIG. 24 is an enlarged top view of the distal end of the surgicalinstrument of FIG. 12, showing the coupling end and attached lockingpin/screw being inserted into the spinal implant, in accordance with anaspect of the present invention;

FIG. 25 is a perspective, exploded view of another embodiment of avertebral body replacement device, in accordance with an aspect of thepresent invention.

FIG. 26 is a front view of the vertebral body replacement device of FIG.25 in accordance with an aspect of the present invention;

FIG. 27 is a cross-sectional, side elevational view of the vertebralbody replacement device of FIG. 25 in accordance with an aspect of theinvention, shown with an insertion instrument in accordance with anaspect of the invention;

FIG. 28 is a cross-sectional, plan view of the vertebral bodyreplacement device of FIG. 25 in accordance with an aspect of theinvention, taken through line 28-28 of FIG. 27;

FIG. 29 is a perspective view of the vertebral body replacement deviceof FIG. 25 in accordance with an aspect of the invention, shown with aninsertion instrument in accordance with an aspect of the invention;

FIG. 30 is an enlarged perspective view of a distal end portion of theinsertion instrument of FIG. 29 in accordance with an aspect of theinvention;

FIG. 31 is another enlarged perspective view of a distal end portion ofthe insertion instrument of FIG. 29 in accordance with an aspect of theinvention, shown with the vertebral body replacement device of FIG. 25;

FIG. 32 is another enlarged perspective view of a distal end portion ofthe insertion instrument of FIG. 29 in accordance with an aspect of theinvention, shown with the vertebral body replacement device of FIG. 25and a tool in accordance with an aspect of the invention;

FIG. 33 is a perspective, exploded view of another embodiment of avertebral body replacement device, in accordance with an aspect of thepresent invention.

FIG. 34 is a front view of the vertebral body replacement device of FIG.33 in accordance with an aspect of the present invention, with the endmembers shown without footplate members attached;

FIG. 35 is an enlarged truncated view of a the vertebral bodyreplacement device of FIG. 33, showing one end member with a footplatemember attached; and

FIG. 36 is a front view of another embodiment of a vertebral bodyreplacement device, in accordance with an aspect of the presentinvention.

DETAILED DESCRIPTION OF EMBODIMENTS

Generally stated, disclosed herein is a vertebral body replacementdevice or vertebral spacer that typically includes a body member, acentral rod member, a support ring, two end members and at least onefootplate member. As used herein, the terms “vertebral body replacementdevice” and “vertebral spacer” may be used interchangeably as theyessentially describe the same type of implant device. Further, describedherein is a surgical method for using the vertebral body replacementdevice to maintain a space between two vertebral bodies within a patientsuffering from a diseased or damaged spinal column.

As depicted in FIG. 1, the general arrangement of a vertebral bodyreplacement device 10, in accordance with an aspect of the presentinvention, includes a body member 30, at least two end members 20, acentral rod member 40 and a support ring 50. In this detaileddescription and the following claims, the words proximal, distal,anterior, posterior, medial, lateral, superior and inferior are definedby their standard usage for indicating a particular part of a bone orprosthesis according to the relative disposition of the natural bone ordirectional terms of reference. For example, “proximal” means theportion of a prosthesis nearest the torso, while “distal” indicates theportion of the prosthesis farthest from the torso. As for directionalterms, “anterior” is a direction towards the front side of the body,“posterior” means a direction towards the back side of the body,“medial” means towards the midline of the body, “lateral” is a directiontowards the sides or away from the midline of the body, “superior” meansa direction above and “inferior” means a direction below another objector structure.

With reference to FIG. 1, vertebral body replacement device 10 includesbody member 30, at least two end members 20 positioned superior andinferior relative to body member 30, a central rod member 40 forplacement within body member 30 and support ring 50 that is configuredto contact and secure central rod member 40 within body member 30.

Exhibited in FIG. 1, body member 30 also includes an inner wall 31 andan outer wall 32, at least one hole 38 extending from outer wall 32through inner wall 31. Further, body member 30 has at least oneanti-rotational rib 35 disposed on and extending for substantially theentire length of outer wall 32. At least one rib 35 is oriented in asuperior to inferior direction relative to body member 30 andsubstantially parallel to a longitudinal axis 72 of body member 30. Atleast one hole 38 is used for the placement of bone graft or otherbiocompatible material that will facilitate bone fusion to occur in vivofollowing implantation of the device. It should be understood to thoseskilled in the art that body member 30 may be available to the operatingsurgeon in various outside diameter sizes and longitudinal lengths L(see FIG. 3). Having multiple sized body members 30 as part of animplant system allows the operating surgeon to use vertebral bodyreplacement device 10 in various levels or segments of the spine (i.e.,smaller sizes in the cervical spine, medium sizes in the thoracic spineand larger sizes in the lumbar spine).

As shown in the cross-sectional view of FIG. 3, body member 30 furtherincludes a first or superiorly positioned end receptacle 33 and a secondor inferiorly positioned end receptacle 34 with longitudinal axis 72extending between these two structures within elongate body member 30. Amiddle chamber 36 is defined by inner wall 31 and is bound superiorly byfirst end receptacle 33 and inferiorly by second end receptacle 34. Atleast one tool port hole 39 extends into middle chamber 36 through outerwall 32 and inner wall 31. In addition, inner wall 31 of middle chamber36 includes a set of internal threads 37 positioned in the bottomportion of middle chamber 36. Internal threads are sized and configuredto threadingly engage the external threads 52 of support ring 50 (notshown). A ceiling surface 74 bounds the superior portion of middlechamber 36 with a centralized opening 75 positioned through ceilingsurface 74. Although not shown, when vertebral body replacement device10 is fully assembled and in use, central rod member 40 is operativelyassociated with body member 30 by being configured to allow for asuperior threaded portion 41 of central rod member 40 to pass throughcentralized opening 75 resulting in a collar element 47 of central rodmember 40 contacting ceiling surface 74. Following placement of superiorthreaded portion 41 of central rod member 40 through centralized opening75, central rod member 40 is moveably secured within middle chamber 36by threadingly coupling support ring 50 to internal threads 37 of middlechamber 36 resulting in a bearing surface 51 of support ring 50 makingpressing contact with a support surface 45 of central rod member 40.Body member 30 further includes at least one locking pin hole 71 (asseen in FIG. 1) that passes through outer wall 32 and inner wall 31 intomiddle chamber 36. Although not shown, following final placement andadjustment of assembled vertebral body replacement device 10, acorresponding threaded pin or bolt may screw into at least one lockingpin hole 71 resulting in central rod member 40 being secured inposition, fixing the overall length of vertebral body replacement 10.

FIGS. 1 and 4 show central rod member 40 having first or superiorthreaded portion 41 and a second or inferior threaded portion 42 withthe two threaded portions having opposing thread configurations. Thismeans that when first threaded portion 41 is constructed withright-handed threads, second threaded portion 42 is constructed withleft-handed threads. It should be understood to those skilled in the artthat the vice-versa thread configuration is also contemplated. Centralrod member 40 further includes a central axis 46 that passes from firstthreaded portion 41 to second threaded portion 42 with a gear wheelportion 43 being positioned intermediate first threaded portion 41 andsecond threaded portion 42. Gear wheel portion 43 is generallyconstructed with a toothed face surface 44, the plane of toothed facesurface 44 being oriented substantially perpendicular to central axis46. Collar element 47 is positioned adjacent to tooth face surface 44 toensure proper external access of tooth face surface 44 within middlechamber 36 following assembly of vertebral body replacement device 10.Further, gear wheel portion 43 includes support surface 45 that islocated on the inferior aspect or underside of gear wheel portion 43.Similar to that described for toothed wheel surface 44, the plane ofsupport surface 45 is correspondingly oriented substantiallyperpendicular to central axis 46. As explained previously, supportsurface 45 will contact and slidingly articulate with bearing surface 51of support ring 50 (see FIG. 1) when vertebral body replacement device10 is assembled and in use. Gear wheel portion 43 is integral to centralrod member 40 and is positioned so that when gear wheel portion 43 ismoved about its rotational axis, first threaded portion 41 and secondthreaded portion 42 will also rotate because gear wheel portion 43 axisof rotation is coaxial with central axis 46.

FIGS. 1, 2A and 2B depict end member 20. Vertebral body replacementdevice 10 includes in its construct at least two end members 20, withthe first one end member 20 being positioned superiorly relative to bodymember 30 and the second end member 20 being positioned inferiorlyrelative to body member 30. In operation, superiorly positioned firstend member 20 is aligned and concentric with first end receptacle 33 sothat when first end member 20 moves relative to body member 30, aninternal wall 23 of end member 20 is continuously positioned adjacent toouter wall 32 of first end receptacle 33. The same operationalrelationship occurs with inferiorly positioned second end member 20 asit will be aligned and concentric with second end receptacle 34 so thatwhen second end member 20 moves relative to body member 30, internalwall 23 of end member 20 is continuously positioned adjacent to outerwall 32 of second end receptacle 34.

As seen in FIGS. 2A and 2B, end member includes an inner portion 21 thatis bounded by internal wall 23 and a centrally positioned threadedhousing element 28. Threaded housing element 28 is constructed withinternal threads 29 that may extend the full length of threaded housingelement 28. Internal threads 29 are configured to correspondinglythreadingly engage threaded portions 41, 42 of central rod member 40upon assembly of vertebral body replacement device 10. Although notshown in FIGS. 2A and 2B, internal wall 23 also includes at least onechannel 25 (see FIG. 1) with at least one channel 25 being orientedsubstantially vertical and is sized to receive corresponding at leastone anti-rotational rib 35 of body member 30 when vertebral bodyreplacement device 10 is assembled.

As further shown in the cross-sectional views of FIGS. 2A and 2B, endmember 20 has an external wall 22, through which at least one hole 27passes to adjacent internal wall 23. At least one hole 27 is sized toallow for the placement of bone graft material and other biocompatiblematerials for the purpose of facilitating a bone fusion bed followingimplantation.

Additionally, as seen in FIGS. 1 and 2A, end wall 24 functions to cap orbound inner portion 21 at one end of end member 20. End wall 24 isintegrally coupled to threaded housing element 28 and generally includesat least one projection 26 or engagement element that extends in anoutward direction from the outer surface of end wall 24. At least oneprojection 26 may be configured as a tooth-like body (as shown in FIGS.1, 2A, 2B, and 5) although other shaped projections or engagementelements are contemplated including, but not limited to spikes, pegs,grids, fingers and posts. At least one projection 26 is sized to allowfor operative engagement with the adjacent vertebral body, morespecifically with the anatomic end plate of the vertebral body toprovide adequate fixation post-implantation and to withstand anytorsional loads that may be applied to end member 20 followingimplantation and during the lengthening procedure of vertebral bodyreplacement device 10.

Cross-section view of FIG. 2A shows, end wall 24 being orientedperpendicular or normal relative to external wall 22. FIG. 2B shows analternative embodiment of end member 20 with end wall 24 being orientedat an angle α and relative to external wall 22. Having end wall 24 beingangled provides the operating surgeon with the ability to treatclinically, lordotic and kyphotic deformities. It should be wellunderstood to those skilled in the art that end member 20 will beoffered in a wide range of degrees of angulations in varying incrementsfrom 0° to 20°, thereby providing the operating surgeon with the abilityto precisely treat any deformity presented during a surgical procedure.

As shown in FIG. 9, it is contemplated that, vertebral body replacementdevice 10 may include an alternative embodiment of end member 90, withend wall 94 being configured to couple a footplate member 80. End wall94 may further include at least one alignment tab 91 that functions toorient footplate member 80 in the preferred position relative to endmember 90 and a vertebral body following implantation. As seen in FIGS.11A and 11B, it is contemplated that footplate member 80 will beavailable in a plurality of various circular, non-circular and polygonalouter profile shapes, (i.e., circular as shown in FIG. 9, oval as shownin FIG. 11A, kidney as shown in FIG. 11B or oblong (not shown)) andsizes. It is further contemplated that footplate member 80 will beavailable in varying thicknesses or heights T as seen in FIG. 10A.Having a kit or implant system that includes a range of various sizedheights, shapes, sizes and angled footplate members 80 provides theoperating surgeon with multiple choices to maximum bone coverage, spinealignment and resulting stability of the device relative to the adjacentvertebral body following implantation.

As shown in FIG. 10A, an end surface 82 may be configured in a neutralor normal orientation relative to a sidewall 83 of footplate member 80.Alternatively, FIG. 10B shows footplate member 80 having end surface 82being angled (angle A) relative to sidewall 83. As discussed above, itis contemplated that the operating surgeon will be provided with aplurality of footplate members 80 each having a different angle, withangulation ranging from 0° to 20°. Having such a wide range ofincrementally angled footplate members 80 available will provide theoperating surgeon with the ability to customize the vertebral bodyreplacement device 10 during the operative procedure to meet thepresented clinical deformity. Although shown with a circular perimetergeometry in FIG. 9, as described previously it should be understood tothose skilled in the art that both neutral and angled footplate members80 will be constructed in multiple outer profile geometric shapes, sizesand overall thickness T, again to provide the operating surgeon with theability to maximize bone support post-implantation. Footplate member 80may be modular in design, thereby allowing the operating surgeon to mixand match and interchange footplate members 80 with end member 90. Thisis accomplished by securely attaching and allowing detachment offootplate member 80 from end wall 94 of end member 90 by use of alocking mechanism 84. For example purposes only, as shown, lockingmechanism 84 may consist of at least one locking screw 85 that passesthrough a hole 87 in end surface 82 to engage corresponding threadedholes 92 in end wall 94. Further, it should be understood to thoseskilled in the art that various other low-profile locking or securementmechanisms may also be used for this purpose including, but not limitedto lock pins, bolts, and press fit pins. As described above, it iscontemplated that footplate member 80 will also include at least oneprojection 86 or engagement element that extends outwardly from the endsurface 82. At least one projection 86 may be configured as a tooth-likeprojection (as shown in FIGS. 9, 10A, and 10B) although other shapedengagement elements are contemplated, including but not limited to,spikes, pegs, grids, figures and posts. End surface 82 may be treated orcoated with certain materials to facilitate bio-ingrowth with theadjacent vertebral body following implantation. Additionally, endsurface 82 may also undergo a process or treatment that results in endsurface 82 having nano-sized or micron-sized surface features. Inaddition, footplate member 80 may have an orientation mechanism 93 thatmay include alignment slots 88 that slidingly engage corresponding tabs91 positioned around the peripheral of end member 90. Orientationmechanism 93 functions to securely orient footplate member 80 relativeto end wall 94 and the adjacent vertebral body.

Following the assembly of vertebral body replacement device 10,superiorly positioned or first end member 20 and inferiorly positionedor second end member 20 are both positioned with each respective innerportion 21 and threaded housing element 28 within first end receptacle33 and second end receptacle 34, respectively. As shown in FIG. 6, firstend member 20 and second end member 20 may be simultaneously extended orretracted in an axial direction relative to body member 30 resulting ineither the lengthening or shortening of the over-all length of vertebralbody replacement device 10 by inserting a tool 70 through tool port hole39 to engage the gear shaped tip (not shown) of tool 70 with tooth facedsurface 44 of gear wheel portion 43 of central rod member 40. Inoperation, tool 70 is rotated causing gear wheel portion 43 to rotateresulting in first and second threaded portions 41, 42 rotating aboutcentral axis 46. When assembled, threaded housing element 28 of firstand second end members 20 are threaded onto first and second threadedportions 41, 42 of central rod member 40 respectively, with at least onechannel 25 of first and second end members 20 also engaging at least oneanti-rotational rib 35 positioned on outer wall 32 of first and secondend receptacles 33, 34, respectively. Functionally, the engagement of atleast one channel 25 of first and second end members 20 with at leastone rib 35 of body member 30 prohibits rotational movement of the firstand second end members 20 when tool 70 is turned, thus resulting infirst and second end members 20 simultaneously advancing or moving inopposing axial directions relative to body member 30 for a maximumdistance equal to the thread length of first and second thread portions41, 42 of central rod member 40. As discussed above, the bi-directionalaxial motion of the first end and second end members 20 is caused by theopposing threads (i.e., right-handed and left handed threads) of therespective first and second threaded portion 41, 42 of the central rodmember 40. Operationally, central rod member 40 converts the rotationalmotion of tool 70 and gear wheel portion 43 into corresponding axial orlinear movement of first and second end members 20, with the mating ofchannel 25 and rib 35 substantially prohibiting any rotational movementof two end members 20 relative to longitudinal axis 72 and the adjacentvertebrae, thus eliminating torsional forces being applied to the endmember-vertebral body interface. For example purposes, FIG. 5 shows anassembled vertebral body replacement device 10 following partialsimultaneous movement of first and second end members 20 as describeabove.

FIG. 8 shows assembled vertebral body replacement device 10 positionedwithin a space between two vertebral bodies following simultaneousmovement of first and second end members 20 in the manner describedabove, resulting in intimate contact between an adjacent vertebral bodyand at least one projection 26 extending from end wall 24, oralternatively, projection 86 of footplate member 80 (not shown). Aresultant compressive force is applied by each end member 20 (orfootplate member 80) against the contacted vertebral body to maintainthe desired anatomic spacing.

The surgical technique for implantation of a vertebral body replacementdevice is well known in the art, including the appropriate surgicalexposure and dissection techniques. The method includes, obtaining avertebral body replacement device 10 that may include body member 30,central rod member 40 that has two threaded portions 41, 42 and isconfigured to be operatively associated within body member 30 and firstand second end members 20 that are configured to threadingly engage thetwo threaded portions 41, 42 of central rod member 40. As discussedabove, body member 30 and end members 20 are further configured toinhibit rotational movement of two end members 20 following assembly andpositioning of vertebral body replacement device 10 within a spacewithin a spinal column with both end members 20 engaging respectivevertebral bodies when central rod member 40 is rotationally actuated,thus causing two end members 20 to move in opposing axial directionsrelative to body member 30. Upon such movement, two end members 20 willapply a force to the two adjacent vertebral bodies within the spinalcolumn. It should be understood that all of the above noted devicecomponents and respective elements include the same structural andfunctionality characteristics as described previously herein.

As seen in FIG. 7, the method may further include the step ofpositioning vertebral body replacement device 10 between two vertebralbodies within a patient's spinal column. The surgical method may alsoinclude the step of simultaneously operatively moving in opposingdirections both end members 20 relative to body member 30 to produce aforce against the two respective adjacent vertebral bodies for thepurpose of maintaining a space between the two vertebral bodies withinthe spinal column as shown in FIG. 8. Although not shown, the method mayfurther include the step of engaging tool 70 with central rod member 40through tool portal hole 39, whereby rotary motion of tool 70 isconverted into opposing axial movement of two respective end members 20relative to body member 30 causing two end members 20 to come in contactand apply a force to the adjacent vertebral bodies, thereby maintainingthe space between these two vertebral bodies. The method also mayinclude the step of securely coupling to body member 30 a lock pinthrough lock pin hole 71 following finalization of the length adjustmentprocedure to ensure securement of two end members 20 relative to bodymember 30 and central rod member 40.

It should be understood by those skilled in the art that the surgicalmethod described herein may also include alternatively, using themodular footplate member 80 that has been coupled to alternativeembodiment end member 90 which has been more fully described above. Thesequence of implantation of vertebral body replacement device 10 asdescribed herein may be different depending upon the given clinicalsituation and whether footplate members 80 are attached on the “backtable” prior to the complete assembly of vertebral body replacementdevice 10 or within the operative site. The sequence of device assemblywill be at the discretion of the operating surgeon and will varydepending upon the preference of the operating surgeon in combinationwith the clinical needs of the patient.

It is further contemplated that an implant system comprised of variouscross-sectional sizes, cross-sectional polygonal and circular/ovalshapes and longitudinal lengths of body members 30, end members andfootplate member 80 will be available as a kit. This will allow theoperating surgeon to pick and choose the separate member components toassemble vertebral body replacement device 10 that best fits into acertain spinal segment or to address an anatomical deformity presentedin a patient. It should be understood by those skilled in the art thateach shaped and dimensioned member provided will function in the samemanner as described previously herein with central rod member 40 andsupporting ring 50.

Also disclosed herein is a surgical instrument for use in inserting animplant into a space between two bones. More specifically, the surgicalinstrument will typically be used to hold, extend/contract and lock avertebral body replacement implant during implantation into the spinalcolumn. The surgical instrument generally includes a handle assembly, anelongate member that includes an implant engagement assembly at thedistal end. The implant engagement assembly further includes anactuation body and an implant holding portion that has two arms thatmove and grasp the implant when the actuation body is actuated. Thesurgical instrument further includes a length control mechanism andlocking mechanism. The distal end or gear assembly of the length controlmechanism is inserted into the implant and couples to a correspondinglength adjustment mechanism to allow for varying the overall length ofthe implant. The surgical instrument typically further includes alocking mechanism that provides for the insertion of a locking pin orscrew into the implant to fix the overall length of the implant.

As used herein, the terms “surgical instrument” and “inserter” may beused interchangeably as they essentially describe the same type ofoperative instrument. Further, described herein is a surgical method forusing the surgical instrument, a method of fabricating the surgicalinstrument and a spinal implant insertion kit that is used to maintain aspace between two vertebrae within a patient suffering from a diseasedor damaged spinal column.

As depicted in FIGS. 12, 14 and 15, the general arrangement of asurgical instrument 11, in accordance with an aspect of the presentinvention, includes a handle assembly 100, an elongate member 201, animplant engagement assembly 204, a length control mechanism 300, and atleast one locking mechanism 400. Surgical instrument 11 is to be used tograsp, expand and contract the length and secure the overall length ofthe implant when placed within the body. One type of implant that may beused with surgical instrument 11 is the one described in U.S. patentapplication Ser. Nos. 11/928,532 and 11/928,553. The contents anddisclosure provided in these U.S. applications are hereby incorporatedherein by reference.

In this detailed description and the following claims, the wordsproximal, distal, anterior, posterior, medial, lateral, superior andinferior are defined by their standard usage for indicating a particularpart of a bone, prosthesis or surgical instrument according to therelative disposition of the surgical instrument or directional terms ofreference. For example, “proximal” means the portion of an instrumentpositioned nearest the torso, while “distal” indicates the part of theinstrument farthest from the torso. As for directional terms, “anterior”is a direction towards the front side of the body, “posterior” means adirection towards the back side of the body, “medial” means towards themidline of the body, “lateral” is a direction towards the sides or awayfrom the midline of the body, “superior” means a direction above and“inferior” means a direction below another object or structure.

With reference to FIGS. 12 and 14, surgical instrument 11 includeshandle assembly 100, elongate member 201, implant engagement assembly204 that further includes an actuation body 205, an alignment body 214and a holding portion 206. Further included in surgical instrument 11 islength control mechanism 300 and at least one locking mechanism 400 thatis oriented to run parallel to a longitudinal axis 210 of elongatemember 201.

As shown in FIG. 12, handle assembly 100 of surgical instrument 11 alsoincludes a body portion 101 and a top portion 102. Body portion 101 isgenerally configured as a grip or holder to accommodate the palm andfingers of the operating surgeon. It is contemplated that body portion101 may be available in varying sizes and configurations to allow forsurgical instrument 11 to be used in a wide range of surgicalapplications, including endoscopic procedures and approaches as well asfit various user hand sizes without sacrificing dexterity and comfort.Centered in top portion and extending in proximal to distal direction isat least one through hole 103. Hole 103 is sized to receive and fix adistal projecting cannulated tube 304 (see FIG. 19) that houses a driveshaft 303 that is a component of length control mechanism 300.

As seen in FIGS. 12 and 19, positioned on either side of hole 103 aretwo substantially parallel through holes 104 that are sized to receivethe connecting rods 403 for the at last one locking mechanism 400. Theembodiment shown for example purposes in FIG. 19, depicts twosubstantially parallel holes 104 that are sized to receive connectingrod 403 of locking mechanism 400. Holes 104 are configured to allowrotary motion of connecting rod 403 when an operating surgeon is usingsurgical instrument 11 to secure the overall length of an implant.

Positioned intermediate handle assembly 100 and actuation body 205 iselongate member 201. FIGS. 12, 14 and 15 show elongate body 201extending in a proximal to distal direction with a first end 202 beinglocated adjacent to handle assembly 100 and a second end 203 beingmoveably or rotatably connected to distally positioned implantengagement assembly 204 or more specifically, to actuation body 205. Asseen in FIGS. 12-15, elongate member 201 is tube-like in structure witha round cross-sectional shape, although it is further contemplated thatvarious geometric shaped cross-sections may be used in constructingelongate member 201, including, but not limited to oval, square, square,rectangular and other polygonal shapes. Further, as shown in FIG. 19,elongate member 201 is hollow with the inner diameter being sized toaccommodate and surround cannulated tube 304. First end 202 is generallyshaped as a gripping portion 211 with the configuration providing theoperating surgeon with increased surface area and texture to grip andturn elongate member 201 when necessary. Second end 203 is typicallyconfigured to include a set of external threads 212 that willthreadingly engage actuation body 205. When the operating surgeonrotates elongate member 201, the engaged to actuation body 205 movesdistally resulting in holding portion 206 engaging and grasping theimplant. If the operating surgeon were to reverse the direction ofrotation of elongate member 201, this would result in engaged actuationbody 205 moving proximally relative to elongate member 201 and causeholding portion 206 to expand and release the implant from between firstand second arms 207, 208.

FIG. 13 is an exploded view that shows implant engaging assembly 204 inmore detail, specifically actuation body 205 and holding portion 206.Actuation body 205 may further be constructed to include a throughcentral hole 220 with internal threads 209 that engage external threads212. At least two through holes 215 are laterally positioned and may besized to receive connecting rods 403. A slotted transverse opening 221that is sized to slidingly engage the alignment body 214 is positionedin the distal aspect of actuation body 205. Connecting holes 222 forcoupling the drive links 213 may also be constructed in the superior andinferior surfaces of the distal aspect of actuation body 205. A throughhole 223 is positioned along the midline of alignment body 214 and it issized to receive cannulated tube 304 and drive shaft 303. In addition,alignment body 214 may include fixation holes 224 that allow for themoveably coupling of arms 207, 208.

Holding portion 206 as seen in FIGS. 16-18 generally includes alignmentbody 214, drive links 213, first arm 207 and second arm 208 withattached engagement members 216 positioned at the distal aspect of thefirst and second arms 207, 207. Holding portion 206 is constructed toallow for first and second arms 207, 208 to move in a direction towardsthe midline of surgical instrument 11 and then away from the midlinewhen drive links 213 are moved either distally or proximally,respectively.

As seen in FIG. 17, drive links 213 are attached to actuation body 205,therefore as discussed above, when elongate member 201 is threaded intoactuation body 205 and move actuation body 205 in either a distal orproximal direction, the distally attached drive links 213 will thencause first and second arms 207, 208 to move either towards the midlineor away from the midline. First and second arms 207, 208 are generallyconfigured as L-shaped bodies to facilitate continuous movement whencoupled to drive links 213.

FIGS. 13 and 17 also depict the two engagement members 216 that arepositioned at the distal ends of first and second arms 207, 208.Engagement members 216 are attached to the distal ends of first andsecond arms 207, 208 in a manner that allows engagement members 216 topivot and rotate around the arm ends. This pivoting motion coupled withthe movability of arms 207, 208 allows surgical instrument 11 toaccommodate a broad range of sizes of implants including implants withvariable widths or diameters. Engagement members 216 have a distalsurface 217 that includes an attached engagement element 218 that issized to engage or mate with a corresponding opening on the exteriorsurface of the implant.

As seen in FIGS. 13 and 17, for example purposes, engagement element 218is configured as a knob-like structure, although it is contemplated thatother protrusion-like structures including, but not limited to springballs, rods or pins may be used.

FIGS. 12 and 15 further show length control mechanism 300 that functionsto engage with the implant and mechanically change the overall length ofthe implant both through extension of the implant and contraction orshortening of the implant. This is generally accomplished by using therotary motion of length control mechanism 300 that mates with acorresponding length adjustment mechanism in the implant. The lengthadjustment mechanism of the implant is designed to convert the rotarymotion of the length control mechanism 300 to translational motion,wherein the overall linear length of the implant is then changed. Lengthcontrol mechanism 300 includes a gripping portion 301 that is positionedat the proximal end of surgical instrument 11. Gripping portion 301 istypically shaped as a knob or other similar structure to allow theoperating surgeon easy manipulation. Gripping portion 301 is connectedto the proximal end of drive shaft 303 that extends generally in aproximal to distal direction and is also substantially parallel tolongitudinal axis 210.

As seen in FIG. 19, drive shaft 303 passes through hole 103 and isencased by cannulated tube 304 within handle assembly 100. Cannulatedtube 304 is sized to allow drive shaft 303 to move in a distal toproximal direction and rotate. Attached to the distal end of drive shaft303 is a gear assembly 302.

FIGS. 13, 15 and 17 show gear assembly 302 extending to a distance thatis generally between arms 207, 208 that enables gear assembly 302 toenter through one of the several holes of the implant to engage thelength adjustment mechanism of the implant. As seen in FIG. 13, gearassembly 302 is secured to the distal end of drive shaft 303approximately proximate to the exit point of drive shaft 303 fromcannulated tube 304. Because of the securement of gear assembly 302directly to drive shaft 303, when gripping portion 301 is rotatedclockwise, this directional motion is directly translated to gearassembly 302 that correspondingly rotates in a clockwise direction. Itshould be noted that length control mechanism 300 may be rotated both ina clockwise and counter-clockwise direction depending on whether thesurgeon is lengthening (expanding) or shortening (contracting) theimplant.

FIGS. 12, 15 and 19 generally exhibit locking mechanism 400. For examplepurposes, surgical instrument 11 as depicted in these figures includestwo locking mechanisms 400, although it is contemplated that only onelocking mechanism may be necessary for securing the overall length ofthe implant post-implantation. As seen in the cross-section view of FIG.19, locking mechanism 400 has a gripping portion 401 that is positionednear the proximal end of surgical instrument 11 and proximate to handleassembly 100. Gripping portion 401 is typically configured as a knob orother handle-like shape to allow the operating surgeon easy grasping andmanipulation when in use. Connected to gripping portion 401 isconnecting rod 403 that extends in a proximal to distal direction andsubstantially parallel to longitudinal axis 210. Connecting rod 401passes through hole 104 in handle assembly 100, with hole 104 beingsized to allow for rotational and translational movement of connectingrod 403 without any impingement. Connected to the distal portion ofconnecting rod 403 is coupling end 402. (See FIG. 13.)

As seen in FIGS. 13, 16 and 18, connecting rod 403 may includetransition portion 408 that may be slightly curved and fabricated from aflexible material to allow for curving of coupling end 402 and entryinto alignment body 214. Examples of possible flexible materials to useto construct transition portion 408 include nitinol or otherelastic/pseudoelastic metals and various compliant polymers, includingbut not limited to polyethylene and polystyrene. Coupling end 402further includes a distal tip 406 that is configured to allow fordetachably coupling of the locking pin/screw following securement withinthe implant. As seen in FIG. 17, distal tip 406 may be shaped as a hexor other geometric shape that would in turn match up with the head ofthe corresponding locking pin/screw.

FIGS. 13, 16 and 17 show further that connecting rod 403 may alsoinclude a bearing portion 407 that slidingly engages with a slot 219that is positioned in the lateral side of alignment body 214. Slot 219is generally sized to allow for rotational and translational movement ofbearing portion 407 while also correctly aligning tip 406 with a hole inthe side of the implant for the insertion of the locking pin/screw.Depending on whether there are one or two locking mechanisms 400 presentin the invention will determine the number of slots 219 present inalignment body 214. Although not shown, it would be understood by oneskilled in the art that the locking pin/screw may include externalthreads for engaging the side hole of the implant or the internal lengthadjustment mechanism. An alternative locking mechanism either on thehead or engagement end of the locking pin/screw may be used to securethe locking pin/screw to the internal length adjustment mechanism of theimplant.

As shown in FIG. 15, surgical instrument 11 may use two lockingmechanisms 400. If this is the case, connecting rods 403 will generallyrun parallel to each over the length of surgical instrument 11. Havingtwo locking mechanisms 400 present allows the operating surgeon tosecure the implant at two locations to ensure long term stability of theoverall length of the implant post-operatively.

The surgical technique for implantation of an implant 700 is well knownin the art, including the appropriate surgical exposure and dissectiontechniques. The method generally includes, obtaining an implant 700 andsurgical instrument 11 that may include handle assembly 100 positionedat the proximal end of surgical instrument 11, elongate member 201having a first end 202 being located adjacent to handle assembly 100 andsecond end 203 connected to implant engagement assembly 204. Surgicalinstrument 11 may further have length control mechanism 300, whichgenerally will be constructed of gripping portion 301, gear assembly 302and drive shaft 303. Surgical instrument 11 may yet further have atleast one locking mechanism 400 that has gripping portion 401, couplingend 402 and connecting rod 403. It should be understood that all of theabove noted instrument components and respective elements include thesame structural and functionality characteristics as describedpreviously herein.

The method may further include the step of coupling implant 700 toimplant engagement assembly 204, or more specifically engagement member216. Implant 700 is grasped or held by surgical instrument 11 when theoperating surgeon places implant 700 between engagement members 216. Theoperating surgeon then rotates either clockwise or counter-clockwiseelongate member 201 via holding gripping portion 211 depending onwhether arms 207, 208 need to be spread farther apart or brought closertogether to make contact with implant 700. The operating surgeon mayforego holding onto the gripping portion 211 and may also turn elongatemember 201 along its shaft as well. Upon rotation of elongate member201, external threads 212 engage internal threads 209 of actuation body205 causing actuation body 205, depending on the direction of rotationof elongate member 201, to move either proximally or distally. Movementof actuation body 205 results in drive links 213 actuating arms 207, 208to either move closer together to grasp the implant or farther apart torelease the implant from between engagement members 216. The pivotingconnection between arms 207, 208 and engagement member 216 allowsholding portion 206 to accommodate and engage a wide range of sizes,configurations and diameters of implants.

As shown in FIG. 20, the surgical method may also include the steps ofinserting surgical instrument 11 and the attached implant 700 throughthe skin opening and positioning the attached implant 700 adjacent to aspace 801 between the two target bones 800. For example purposes only,as seen in FIG. 20, the two bones may be vertebral bodies or vertebrae800.

FIGS. 21 and 22 exhibits a possible further step of the method, theextension or contraction of the overall length of implant 700 until thetwo ends 705 (Not Shown) of implant 700 make contact with vertebrae 800resulting in a force being applied by implant 700 to maintain the spaceopening between the two vertebrae 800. The overall length of implant 700may be extended or contracted (shortened) by rotating length controlmechanism 300 either in a clockwise or counter-clockwise direction.Following the engagement of implant 700 with holding portion 206 ofsurgical instrument 11, the operating surgeon will push gripping portion301 in a proximal direction resulting in drive shaft 303 and attachedgear assembly 302 also moving proximally, with gear assembly 302entering hole 702. Although not shown, gear assembly 302 will uponmoving into the inner part of implant 700 engage a correspondinglyconfigured length adjustment mechanism. Once gear assembly 302 isengaged with the length adjustment mechanism, the operating surgeon willturn gripping portion 301 either in a clockwise or counter-clockwisedirection. When gripping portion 301 is rotated, drive shaft 303 andconnected gear assembly 302 will also rotate. As described in theabove-noted pending applications that have been incorporated herein byreference, length adjustment mechanism of implant is configured toconvert the rotational movement of gear assembly 302 into translationalmovement within the implant. Essentially, when length control mechanism300 is rotated in one direction implant 700 will extend or get longerand rotating length control mechanism 300 in the opposition directionwill shorten or contract implant 700 while implant is placed between twobones. This novel functionality provides the operating surgeon with theability to accurately adjust and ensure proper implant sizing withoutcompromising positioning within the operative space.

FIGS. 22 and 23 show further the possible step of fixing or securing theoverall length of implant 700 by the insertion of locking pins/screws405 into holes 704 of implant 700 once the appropriate overall lengthhas been determined. The operating surgeon uses locking mechanism 400 byinitially coupling locking pins 405 to tips 406 (Not Shown). Followingthe final positioning and sizing of the implant in vivo, the operatingsurgeon will hold and turn gripping portion 401 that in turn rotatesconnecting rod 403. Depending on the locking or thread configuration oflocking pin 405 and hole 704, gripping portion 401 may be turned eitherin a clockwise or counter-clockwise direction. Gripping portion 401 isthen pushed in a proximal direction causing locking pin 405 to enterhole 704 and engage either threads or another securement configurationwithin implant 700. Following the rotational insertion of locking pin405 into hole 704, the length adjustment mechanism will be locked inplace, thereby fixing the overall length of implant 700. Once lockingpin 405 is fully seated, the operating surgeon will move lockingmechanism 400 in a distal direction and uncouple tip 406 from lockingpin 405.

It should be understood by those skilled in the art that the surgicalmethod and use of surgical instrument 11 described herein may beperformed using either anterior, posterior or lateral approaches to theexample spinal column. In addition, an operating surgeon may use aminimally invasive surgical approach and employ surgical instrument 11because of the multi-functionality (i.e., grasp, extend/contract andlock) operation of surgical instrument 11 relative to implant 700. It isfurther contemplated that surgical instrument 11 may be sized to allowfor endoscopic insertion. Having these multiple functions incorporatedinto one instrument addresses a long felt need of providing theoperating surgeon with the ability to keep one instrument in the woundand to not have to repeatedly remove the instrument and replace it witha different instrument to perform another function. Having amulti-purpose surgical instrument will lessen the potential for tissuedisruption and adjacent structural damage.

It is further contemplated that a method of fabricating surgicalinstrument 11 may include the steps of providing handle assembly 100with an additional step of providing elongate member 201 with one end202 of the elongate member 201 being positioned adjacent to handleassembly 100 and second end 203 of elongate member 201 being moveably orthreadingly connected to implant engagement assembly 204. Rotationalmovement of elongate member 201 relative to handle assembly 100 andimplant engagement assembly results in the grasping and holding of theimplant between engagement members 216.

The fabrication method may also include the further step of providing alength control mechanism 300 that typically allows the operating surgeonto adjust the overall length of the implant while holding the implant inplace between engagement members 216. Yet a further step of the methodmay include providing at least one locking mechanism 400 for thesurgical instrument 11. Locking mechanism 400 permits the operatingsurgeon with the ability to secure and fix the overall length of theimplant after the final positioning and sizing is accomplished in vivo.

It is further contemplated that a spinal implant insertion kit comprisedof various cross-sectional sizes, cross-sectional polygonal andcircular/oval shapes and longitudinal lengths of implants and acorresponding surgical instrument 11 will be available as a kit. Thiswill allow the operating surgeon to pick and choose these modularcomponents that are necessary to assemble a spinal implant that bestfits into a certain spinal segment or to address a certain anatomicaldeformity presented in a patient. The kit would further include a singleinserter 11 that may be used with the multiple sized (both length anddiameter) spinal implants. It is also contemplated that multiple sizedinserters may be included in the kit to accommodate the various anatomicregions of the spine and the corresponding implant sizes (i.e., lumbar,thoracic and cervical). Inserter 11 includes handle assembly 100,elongate member 201, length control mechanism 300 and at least onelocking mechanism 400. For brevity sake, all of the above noted insertercomponents and respective elements will not be discussed again here andinclude the same structural and functionality characteristics asdescribed previously herein.

Referring now to FIGS. 25-36, a vertebral body replacement device 1000in accordance with another exemplary embodiment of the invention isshown. Vertebral body replacement device 1000 includes a body member1100, a central rod member 1200, a first end member 1300 and a secondend member 1400. Those skilled in the art will observe that body member1100, central body member 1200, first end member 1300 and second endmember 1400 have features that correspond to features shown anddescribed above with reference to device 10. Therefore, the descriptionsof corresponding components and features on device 10 are incorporatedby reference into this section.

As with device 10, body member 1100 has an inner wall 1101 and an outerwall 1102. Outer wall 1102 features a plurality of tool ports 1103 thatextend from outer wall 1102 through inner wall 1101. The plurality oftool ports 1103 are arranged along a portion of the perimeter 1110 ofbody member 1100. Outer wall 1102 is configured for engagement with atool, such as a driver tool operable to expand vertebral body device1000. First end member 1300 and second end member 1400 each have endwalls 1350 and 1450, respectively. End walls 1350 and 1450 each featureprojections or spikes 1352 and 1452, respectively. Projections 1352 and1452 are configured to engage a vertebral body when vertebral bodyreplacement device 1000 is fully expanded, or almost fully expanded, ina space between two vertebrae. Body member 1100 may be available to theoperating surgeon in various outside diameter sizes and longitudinallengths, like body member 30.

Central rod member 1200 includes a first threaded portion 1210 and asecond threaded portion 1220. Central rod member 1200 is configured tobe operatively associated within body member 1100, and includes a gearwheel portion 1230. Gear wheel portion 1230 includes a toothed surface1232 and a support surface 1234. Toothed surface 1232 includes acircular arrangement of gear teeth 1233 that surround central rod member1200. Support surface 1234 is separated from toothed surface 1232 by arecessed section 1236.

The plurality of tool ports 1103 on body member 1100 includes a firsttool port 1110, a second tool port 1120 and a third tool port 1130.Third tool port 1130 is positioned between first tool port 1110 andsecond tool port 1120. Gear teeth 1233 of gear wheel portion 1230 areexposed through third tool port 1130 when central rod member 1200 isoperatively associated within the body member, as shown in FIG. 26.Third tool port 1130 is configured to receive a drive shaft 2010 of asurgical instrument 2000, as shown in FIGS. 27 and 30. Drive shaft 2010has a distal end 2020 that includes a gear mechanism 2022. Gearmechanism 2022 includes a plurality of teeth 2024 that are individuallyconfigured to fit between adjacent teeth 1233 on toothed surface 1232.When drive shaft 2010 is inserted through third tool port 1130, and whengear mechanism 2022 is engaged with toothed surface 1232, vertebral bodyreplacement device 1000 can be expanded or retracted in response torotation of the drive shaft.

Body member 1100 includes a first or superiorly positioned endreceptacle 1133 and a second or inferiorly positioned end receptacle1134. A longitudinal axis 1137 extends between end receptacles 1133 and1134. A middle chamber 1136 extends between first end receptacle 1133and second end receptacle 1134. First tool port 1110, second tool port1120 and third tool port 1130 all extend through outer wall 1102 andinto middle chamber 1136.

First end member 1300 is configured to threadingly engage first threadedportion 1210 of central rod member 1200. Similarly, second end member1400 is configured to threadingly engage second threaded portion 1220 ofcentral rod member 1200. As will be described in more detail below, bodymember 1100, first end member 1300 and second end member 1400 includefeatures that inhibit rotational movement of the first and second endmembers relative to the body member when central rod member 1200 isrotationally actuated to move the first end member and the second endmember in an axial direction relative to the body member.

Proper engagement between drive shaft 2010 and toothed surface 1232allows vertebral body replacement device 1000 to be expanded withminimal mechanical resistance or jamming of parts. Should the surgeonexperience excessive mechanical resistance upon rotating the drive shaft2010, this resistance can interfere with the surgeon's ability to sense,by tactile feel, when vertebral body replacement device 1000 iscompletely expanded. Resistance can be caused by improper positioning ofthe drive shaft 2010 relative to toothed surface 1232. Although therelative position of drive shaft 2010 can be controlled by controllingthe shape and size of the tool port that receives the drive shaft, acertain amount of clearance between the drive shaft 2010 and edge of thetool port must be provided to facilitate insertion of the drive shaft.If the axial position of the drive shaft 2010 is not firmly secured, theclearance can allow the drive shaft 2010 to move slightly after it isinserted through the tool port. Any such movement can cause the driveshaft 2010 to move out of proper engagement with toothed surface 1232,leading to an improper engagement and mechanical resistance.

To reduce or prevent the potential for mechanical resistance caused bymisalignment between the drive shaft and toothed surface, vertebral bodyreplacement devices in accordance with the invention preferably includean alignment and indexing mechanism. The alignment and indexingmechanism ensures that the teeth on the drive shaft are properly indexedand engaged with the gear teeth on the toothed surface after the driveshaft is inserted through a tool port. The alignment and indexingmechanism also ensures that the teeth on the drive shaft remain properlyindexed and engaged with the gear teeth on the toothed surface. This isaccomplished by providing one or more engagement points on the outerwall of the vertebral body. The engagement point or points are locatedand configured to mate and lock with engagement elements on a surgicalinstrument, only when the surgical instrument and drive shaft arepositioned in the correct location to properly engage the toothedsurface.

FIG. 26 shows an alignment and indexing mechanism 1500 in accordancewith one exemplary embodiment of the invention. Alignment and indexingmechanism 1500 is formed by the first tool port 1110 and the second toolport 1120. First and second tool ports 1110 and 1120 are positioned onopposite sides of third tool port 1130, and are equidistant from thefirst and second end members 1300 and 1400. Each of the first and secondtool ports 1110 and 1120 have an elongated configuration and isconfigured to cooperate with a corresponding alignment and indexingfeature on the surgical instrument 2000.

Referring now to FIGS. 29-31, surgical instrument 2000 includes analignment and indexing feature 2200 that includes two engagement members2216. Engagement members 2216 are similar in many respects to engagementmembers 216 described above, insofar as both sets of engagement memberscan be moved toward one another to grasp an implant. Each engagementmember 2216 includes an engagement element in the form of a pin 2218. Asleeve 2230 surrounds engagement members 2216, engaging an outer edge2217 of each engagement member. Engagement members 2216 are axiallydisplaceable relative to sleeve 2230 in a proximal direction, in whichthe engagement members are drawn into the sleeve, and a distaldirection, in which the engagement members are extended out of thesleeve. As such, engagement members 2216 move inwardly toward oneanother and converge together in response to being drawn proximally intosleeve 2230, and move outwardly and away from one another in response tobeing extended distally out of the sleeve. Engagement members 2216 aremovable toward one another until they reach a position in which pins2218 are located in a clamping position. Engagement members 2216 can bedisplaced away from one another to spread pins 2218 apart until the pinsreach a release position.

First and second ports 1110 and 1120 are positioned to receiveengagement pins 2218 on instrument 2000. The elongated geometry of firstand second ports 1110 and 1120 are such that pins 2218 can reside in thefirst and second ports when the pins are in either the clamping positionor a release position. Each pin 2218 is centered between top and bottomedges of one of the first and second ports 1110 and 1120. This sets theproper orientation and position of drive shaft 2010 so that gearmechanism 2022 of the drive shaft properly engages the toothed surfaceof gear wheel portion 1230. In particular, first and second slots 1110and 1120 control the position of drive shaft 2010 as it is insertedthrough third tool port 1130, so that teeth 2024 are at the preciseposition and orientation required to index with and fit between teeth1233 on toothed surface 1232. This ensures proper engagement betweendrive shaft 2010 and gear wheel portion 2130 with minimal mechanicalresistance. Pins 2218 also make it easier to re-attach instrument 2000to implant 1000 in the event that the instrument is disconnected fromthe implant during insertion. Ordinarily, it can be very difficult tonavigate a driver instrument into an incision and realign theinstrument's driver tip in situ with the gear mechanism in the implant.Pins 2218 and first and second ports 1110 and 1120 make reconnectionmuch simpler, because the engagement of the pins with the first andsecond ports sets the proper orientation for the drive shaft.

Engagement between vertebral body replacement device 1000 and surgicalinstrument 2000 is enhanced by a “dovetail” projection 1105 on outerwall 1102. Dovetail projection 1105 is formed by a pair of parallelchannels 1106 in outer wall 1102. Each channel 1106 has a V-shapedcross-sectional profile and folios a pointed edge 1107 on each side ofdovetail projection 1105. Engagement members 2216 have V-shaped notches2219 that geometrically conform to pointed edges 1107. When engagementmembers 2216 are moved toward the clamping position, V-shaped notches2219 lockingly engage pointed edges 1107. In this condition, vertebralbody replacement device 1000 is securely gripped by instrument 2000 withdrive shaft 2010 positioned to properly engage the toothed surface. Thesecure engagement prevents drive shaft from shifting or slipping out ofthis position, ensuring that proper indexing and engagement aremaintained.

Referring again to FIGS. 25 and 26, vertebral body replacement device1000 includes a locking mechanism 1600 to fix the position of theimplant after it is expanded to a desired height. Locking mechanism 1600includes a pair of tool ports in the form of locking pin holes 1610 and1612. Locking pin holes 1610 and 1612 are similar to locking pin hole 71discussed above. Locking pin hole 1610 is formed in first end member1300 at a location that is superior to third tool port 1130. Locking pinhole 1612 is formed in second end member 1400 at a location that isinferior to third tool port 1130. Each locking pin hole 1610 and 1612contains a locking element in the form of a threaded locking pin orscrew 1620. Each locking pin 1620 has an outer thread 1622 that engagesan inner thread 1616 inside each of the locking pin holes 1610 and 1612.

First end member 1300 includes an outer wall 1310, and second end member1400 includes an outer wall 1410. The interior of first end member 1300is preferably identical or substantially identical to the interior ofsecond end member 1400. For brevity, the interior of first end member1300 will be described, with the understanding that the features insidefirst end member 1300 are also present inside second end member 1400.Referring to FIG. 28, the interior of first end member 1300 is shown.Inner thread 1616 extends along an inner wall 1615 of locking pin hole1610 and terminates at a terminal point 1617. Terminal point 1617 isrecessed inside and spaced from outer wall 1310. Locking pin 1620 isconfined to locking pin hole 1610 and cannot be advanced past terminalpoint 1617. As such, locking pin 1620 cannot be removed from locking pinhole 1610 through outer wall 1310.

First tool port 1110, second tool port 1120, third tool port 1130,locking pin hole 1610 and locking pin hole 1620 are located in closeproximity to one another on the same side or “segment” of the implant.The term “segment”, as used herein, means a section of the implant thatis defined when a plane is passed through the implant parallel to and incoincidence with the implant's longitudinal axis. The term “longitudinalaxis”, as used herein, means the axis that extends through a centerpoint of each end wall of the implant. FIG. 28 shows a plane P passingthrough longitudinal axis L of implant 1000, defining two segments S1and S2. First tool port 1110, second tool port 1120, third tool port1130, locking pin hole 1610 and locking pin hole 1620 are all located inclose proximity to one another in segment S1, seen best in FIG. 26. Theclose arrangement of the tool ports and locking pin holes on the samesegment allows different instruments to engage the implant from the sameapproach angle. FIG. 32 shows surgical instrument 2000 engaging firsttool port 1110, second tool port 1120 and third tool port 1130 (thesecond and third tool ports being behind the instrument and not visiblein the Figure). A separate driver instrument 3000 is shown beinginserted into locking pin hole 1610 to engage one of the locking pins1620.

Referring back to FIG. 25, vertebral body replacement device 1000includes a C-shaped support ring 1050. Support ring 1050 has a bearingsurface 1051 that contacts central rod member 1200 when the central rodmember is operatively positioned within body member 1100. Supportsurface 1234 of gear wheel portion 1230 is configured to contact bearingsurface 1051 of support ring 1050 when central rod member 1200 isoperatively positioned within the body member. Central rod member 1200has a central axis 1201 extending between first threaded portion 1210and second threaded portion 1220. Gear wheel portion 1230 has arotational axis 1231 that is substantially coaxial to central axis 1201.In this arrangement, as gear wheel portion 1230 is rotated aboutrotational axis 1231, first and second threaded portions 1210 and 1220correspondingly rotate about central axis 1201.

First end member 1300 includes an internal wall 1320, an end wall 1330,and a travel limiting mechanism in the form of a pair of pins 1340.Similarly, second end member 1400 includes an internal wall 1420, an endwall 1430 and a travel limiting mechanism in the form of a pair of pins1440. First end member 1300 has a pair of pin holes 1341 for receivingpins 1340, and second end member 1400 has a pair of pin holes 1441 forreceiving pins 1440. Body member 1100 includes a first pair oflongitudinal slots 1140 adapted to receive pins 1340 and a second pairof longitudinal slots 1150 adapted to receive pins 1440. Pins 1340 and1440 align with and engage first and second longitudinal slots 1140 and1150 when the implant components are assembled. The engagement of pins1340 with the first longitudinal slots 1140 prevents first end member1300 from rotating relative to body member 1100. Similarly, theengagement of pins 1440 with second longitudinal slots 1150 preventssecond end member 1300 from rotating relative to body member 1100. Firstlongitudinal slots 1140 have terminal ends 1142 that limit how far pins1340 can travel, and second longitudinal slots 1150 have terminal ends1152 that limit how far pins 1440 can travel. In this arrangement, pins1340 and 1440, in combination with first and second longitudinal slots1140 and 1150, limit how far the first and second end members can beexpanded relative to body member 1100.

First and second end members in accordance with the invention mayinclude one or more holes disposed in at least one of the external walland the end wall and extending therethrough to allow for the placementof bio-compatible material within the first and second end members. Bodymembers in accordance with the invention also may include one or moreholes for receiving compatible material within the body members. Forexample, first end member 1300 includes multiple tool ports 1305, andsecond end member 1400 includes multiple tool ports 1405. Body member1100 also includes multiple tool ports 1105. Tool ports 1305, 1405 and1105 are configured and positioned to receive bone graft and otherbio-compatible material into various areas inside the implant. Toolports 1305, 1405 and 1105 are also configured to receive impactor toolsto pack in bone graft material within the spaces inside implant 1000.

Referring now to FIGS. 33-36, a vertebral body replacement device 5000is shown in accordance with another exemplary embodiment of theinvention. Vertebral body replacement device 5000 is similar in manyrespects to device 1000, but features a modular first end member 5300and a modular second end member 5400 that attach to footplates 5500.First and second end members 5300 and 5400 cooperate with a body member5100 and a central rod member 5200.

First end member 5300 and second end member 5400 are identicallyconfigured. Therefore, only first end member 5300 will be described withthe understanding that the features of first end member 5300 are alsopresent on second end member 5400. Referring to FIG. 35, footplate 5500is shown detachably coupled to first end member 5300. First end member5300 includes a circular projection 5310 with an annular groove 5320.Each footplate 5500 has a central opening 5510 and an inner slot 5520that carries an elastically deformable snap ring 5530. To attachfootplate 5500 to first end member 5300, the footplate is placed overthe first end member and pushed downwardly onto circular projection 5310so that the circular projection extends into central opening 5510. Asfootplate 5500 is pushed down onto first end member 5300, snap ring 5530expands radially outwardly in response to contact with the exterior ofcircular projection 5310, and remains in an expanded condition in whichit slides over the exterior of the circular projection. In the expandedcondition, snap ring 5530 maintains stored energy until the snap ringaligns with annular groove 5320. Once snap ring 5530 aligns with annulargroove 5320, the snap ring is released from the expanded condition andretracts into the groove toward a more relaxed state. In this position,snap ring 5530 extends in both annular groove 5320 and slot 5520 todetachably couple footplate 5500 to first end member 5300.

The first and second end members 5300 and 5400 in FIG. 33 are modular,as noted above, in that they can connect with footplates, likefootplates 5500. In contrast, first and second end members 1300 and 1400in FIG. 25 have a “unitary” design. That is, they have end walls thatdirectly engage vertebrae, and do not connect to footplates. It will beapparent to those skilled in the relevant art that variousmodifications, additions and substitutions can be made to these featuresand other features in accordance with the invention. With regard to theend members, vertebral body replacement devices in accordance with theinvention need not have first and second end members that areidentically configured. FIG. 36 shows a vertebral body replacementdevice 6000 in accordance with another embodiment of the invention thatfeatures different end member configurations. The first end member 6300is modular, while the second end member 6400 is unitary.

Although the detailed description and drawing figures describe and showspecific embodiments, it will be apparent to those skilled in therelevant art that various modifications, additions and substitutions canbe made without departing from scope of the invention. Any suchmodifications, additions and substitutions are therefore to beconsidered within the scope of the following claims.

What is claimed is:
 1. A vertebral body replacement device having alongitudinal axis and comprising: a first member and a first footplatedetachably connectable to the first member; a second member and a secondfootplate detachably connectable to the second member; and a centralmember detachably connectable to the first member by a threadedconnection, the first member being axially displaceable relative to thesecond member in response to rotational motion of the central memberrelative to the first member so as to adjust an overall length of thevertebral body replacement device, the first footplate comprising afirst surface oriented toward the first member, a second surfaceopposite the first surface and oriented away from the first member, anda sidewall extending between the first surface and the second surface,the first surface comprising an alignment slot facing the first member,the alignment slot is open through the sidewall of the first footplateand configured to slidingly engage the first member to securely orientthe first footplate relative to the first member.
 2. The vertebral bodyreplacement device of claim 1, wherein the central member comprises agear wheel portion having a tooth surface.
 3. The vertebral bodyreplacement device of claim 2, wherein the tooth surface is arranged ona plane that is substantially perpendicular to the longitudinal axis ofthe vertebral body replacement device.
 4. The vertebral body replacementdevice of claim 1, wherein the first member comprises a fastener holeand the first footplate comprises an aperture configured to align withthe fastener hole when the first footplate is connected to the firstmember.
 5. The vertebral body replacement device of claim 4, furthercomprising a fastener configured for insertion through the aperture ofthe first footplate and into engagement with the fastener hole of thefirst member to connect the first footplate to the first member.
 6. Thevertebral body replacement device of claim 4, wherein the aperturecomprises a perimeter edge, at least a portion of which is circular. 7.The vertebral body replacement device of claim 1, wherein the firstfootplate has a circular outer profile shape.
 8. The vertebral bodyreplacement device of claim 1, wherein the first footplate has anon-circular outer profile shape.
 9. The vertebral body replacementdevice of claim 1, wherein the first footplate has an oblong outerprofile shape.
 10. The vertebral body replacement device of claim 1,wherein the second surface of the first footplate comprises at least oneprojection extending outwardly from the first footplate.
 11. Thevertebral body replacement device of claim 10, wherein the at least oneprojection comprises a spike.
 12. The vertebral body replacement deviceof claim 10, wherein the at least one projection comprises a toothprojection, the tooth projection having a width and a height that isless than the width.
 13. The vertebral body replacement device of claim10, wherein the at least one projection comprises a plurality ofprojections.
 14. The vertebral body replacement device of claim 13,wherein the plurality of projections are arranged around a periphery ofthe first footplate.
 15. The vertebral body replacement device of claim13, wherein the plurality of projections comprise a pair of firstdiametrically opposed projections and a pair of second diametricallyopposed projections, the pair of second diametrically opposedprojections angularly offset from the pair of first diametricallyopposed projections.
 16. The vertebral body replacement device of claim15, wherein the pair of first diametrically opposed projections areangularly offset from the pair of second diametrically opposedprojections by an angle of ninety degrees.
 17. The vertebral bodyreplacement device of claim 13, wherein the plurality of projections areequidistant from the longitudinal axis of the vertebral body replacementdevice.
 18. The vertebral body replacement device of claim 1, furthercomprising a plurality of optional footplates, each optional footplatebeing interchangeable with the first footplate or the second footplate.19. The vertebral body replacement device of claim 18, wherein theplurality of optional footplates vary in outer profile shape.
 20. Thevertebral body replacement device of claim 1, wherein the alignment slotis defined by a first slot wall, a second slot wall opposite the firstslot wall, and a third slot wall that interconnects the first slot wallwith the second slot wall, the alignment slot adapted to receive thefirst member between the first slot wall and the second slot wall to fixthe orientation of the first footplate relative to the first member.